Bugs ..... gotta kill the Bugs.
Seriously, scale or mealy bugs can leave those types of marks. Even if you can't see the insect itself the damage is enough evidence to go ahead and treat for insect infestation.
Given that mealy bugs often attack root systems, I would consider bare-rooting the plant, then spraying leaves and roots for bugs, then repotting.
Im interested to see what peoples thoughts on the nutrient deficiency Candace mentioned are. This year most everything went into CHC for me, including my first roth from OI that is BS. It has been growing roots like gangbusters, put up a new leaf, and seemingly been healthy. About three weeks ago I noticed it was looking yellow (its tough to tell sometimes since I grow under lights and the color is always off), and it has the same "yellow throat" is the crown that Ayreon's does. It also dropped its lowest leaf (it may have been its time) and I don't like how yellow the lowest leaf is getting. So I thought must be a nitrogen problem, so along with my phrags it got a light dusting of a 1/2 & 1/2 blood and bone meal mix two weeks ago, but im not seeing any "greening up". Is it something else? I use RO water and fertilize with "Jack's fert. for RO" to a solution of 225-250 ppm and occasionally do spot sprays with pure RO water on all the plants...are we starving them to death?
Scooby, epsom salts will help green them up but I must admit, I have several sanderianum crosses that still look to have a nutrient deficiency no matter what I do. I don't know if they are plain getting to much sun or what. But they are fertilized and in the same sun as all my other paphs yet have the yellowish cast to them. The epsom salts have helped, but not as much as I'd like. None of my other paphs have this, so I'm assuming it has to do with the sanderianum parent and it's needs not being met fully.
Now in your case, there's a thread running currently about using CHC and problems using it-have you read it? I don't know if it will help you or confuse you...
Some kind of virus that also started with pale dots killed 80% of my Phalaenopsis collection... so if you think bugs did this.. well, then that's actually some kind of relief. I have already sprayed the plant and the plants around it. I hope it will help.